has part has part characteristic of part of has modifier Abnormal cardiac septum morphology Atrioventricular canal defect During atrioventricular valvuloseptal morphogenesis, the endocardial cushions expand as they are infiltrated by extracellular matrix secreted from the surrounding myocardium. The cushions then fuse and are remodeled to form the atrioventricular valves and septa. Failure of this process results in AVSD, with the degree of severity dependent on the stage at which the developmental failure occurs. AVSD are a spectrum of cardiac malformations that result in a persistent common atrioventricular canal. quality abnormal atrioventricular canal